Illumination system



oct. 14, 1947. G, H, EVANS' 2,428,792

ILLUMINATION SYSTEM F11ed June 28, 1945 lll 1&1 l '29 'Patented Oct. 14, 1947 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 1 Claim.

The present invention relates to illuminated indicators particularly such as must be readily observable by daylight illumination and at night by artificial illumination without detriment to the observers darkness adaptation. The invention is therefore of special utility in the indicating instruments of moving vehicles such as ships, airplanes, automobiles and the like, where the users vision must be directed alternately to the instrument and to an outside eld of observation highly illuminated at day and poorly illuminated at night. To this end it is desirable that the indicia have good daylight reiiecting qualities to compete in visibility with the highly illuminated outside field, and that at night just those elements indispensable to the reading of the indicator such as indicia and a pointer or selected portion of the latter cooperating with the indicia, be softly but distinctly illuminated f against a dark background and without glare or unwanted reflections of any kind from such background.

The invention seeks as its main object the provision of an illuminating system lfor indicators in which the aforesaid desired qualities are attained in high degree.

An important object is the provision of an indicating instrument in which the above mentioned qualities are attained through an extremely simple and sturdy cooperative combination and arrangement of elements requiring a minimum of highly skilled mechanical workf manship and a minimum of operations in its construction, and in which the operation in use depends mainly upon the characteristics and qualities of the material from which the elements are formed and the `cooperative arrangement of such elements, rather than critical form, dimension and mechanical relation.

Various other objects and advantages of the invention will become apparent from a perusal of the following specification and the drawings accompanying the same.

In the drawings:

Fig. 1 is a top plan View of an indicator dial structure embodying the invention, showing a portion of the cover broken away.

Fig. 2 is a portion of a section on the line 2--2 of Fig. l, on an enlarged scale.

Fig. 3 is a fragmentary side view looking from the left of Fig. 2 with the side wall elements removed.

Referring to the drawings in detail, these show the dial and pointer structure of an indicating instrument in which the indicator shaft I0 of a speed indicator or other responsive device not shown, carries `a pointer arm II arranged to sweep over a dial I2 having a dark colored nonfluorescent surface bearing indicia I3 of uores- Acent material, Preferably the pointer arm II also has a black or dark colored non-fluorescent surface and carries a pointer element I4 of fluorescent material. Thus is avoided the presence of relatively brightly illuminated areas other than those necessarily visible for a reading of the indicating instrument. Preferably the fluorescent material of both the indicia and the pointer element is one which is normally of a substantially yellow color of high visibility and which iluoresces a similar yellow color upon excitation of ultra-violet light. In the present embodiment of the invention the fluorescent material is normally a :bright yellow color of high visibility which upon excitation by ultra-violet light fluoresces a bright yellow very similar to the normal color but appearing to be a little nearer the orange in very slight degree. A circular base member I5 preferably of light material such as wood, compressed fiber, or plastic material covered with a sheet I6 of metal, supports the dial I2.

A source of ultra-violet light for excitation of the fluorescent material of the indicia and pointer element is provided in the form of a series of ultra-violet argon electric bulbs II and ultra-violet transmitting filter elements I8 mounted on the base member I5 around the outer edge of the dial. These filter elements I8 are held in place by the end supports I9 secured to the base member I5 by laterally extending lugs 20 and screws 2|. An annular sheet metal band 22 and annular side wall casing element 23 form the outer side wall of the dial casing, and with the outer marginal portion of the base cover-sheet I6 and an annular sheet metal reflecting ring 24, form an annular inwardly-facing reflector trough 25 for the circular arrangement of lamps I1. To enhance the reflecting eiiiciency of the light trough the sheet material from which the base covering IE, annular band 22 and ring reflector 24 are formed, is preferably aluminum or an aluminum alloy with a highly polished surface on the side next the light, which material has bene found to be of relatively high eciency in reflection of ultra-violet light. The lamps I l are housed within a continuous annular reflecting trough 22 extending around the periphery of the dial and facing inwardly toward the dial with a substantially annular, iilter wall between the open end of the trough and the dial and pointer to be illuminated. Inasmuch as stitution for the argon lamps I1, other lightv sources rich in ultra-violet and performing an equivalent function in the combination. may beY used, such as mercury vapor lampsorhigh-tem.- perature metallic filament lamps. For 'lightproong of the joints between the ends of. filter,

elements i8 suitable soft packing material such as the pieces of felt 26 may bev placed betweenA the adjacent edges of the filter end supports I9.l For light-proofing the joints at top and bottom of the lter elements, light-proofing rings 2'1l and 28' of soft felt or other suitable material are provided. Thus all lightpassing from the bulbs I7- and the reecting Walls'of the trough 25fto the fluorescent indicia and pointer element'mustrpass through the filler elementsv I8 which later operate to cut ofl most of the visible light;

To protect an observersieyes from direct or reiiected ultra-violet radiation whichl would produce the effec-t of a haze in the field of vision due to slight fluorescence within the eyes,` a ray-filter cover 29 is mounted over the dialin overlapping relation with the inner marginal portion of the ring reflector 24". This filter cover is of clear plastic material of a yellow 'color which will' pass both the normal yellow color andthe fluorescent yellow color ofthe indicia and pointer elements., andV cut' off ultra-violet and substantially all` of any visible violet or low` blue that might be passed by the lter elementsl. Thistype o`f-Yye1low filter serves the additional function of protecting' the fluorescent material from the ultra-violet raysofthe sun which hav'e been found to accelerate the decay of iiuorescent paints.

The dial has a mat surface dark in colorpref-v erably black and non-fluorescent. This surface quality is obtained by fthe use of a suitable coatingof paint or the like. It also mayA be V'obtained by forming the vdial of a-dark colored material with amat surface; The dial being'nor'i-fl'l'iorescent, any light passing: therefrom toward the observer can be only'suchlittleas-mightbe reflected from the mat surface 'of thedial' andi this beingv originally only that small amount of visible violet or low blue as may be passed-by the lter, willbe eifectivelyblocked olif by the Vyellow cover filter 29, A clear colorless cover'glass 30! covers the filter-Window element' `29and with the lter 29- is held infplace in therecessformed'bv the spacing'ring 3lbetween thetop reiiecting ringv 24 and thebezelring 32.- This cover assemblage is held together'by suitable screws 33.*pass'ingfthroughthe top reflectingring 2li-and spacing ring 3-into the bezel ring 32'. Th'e'cove'r assemblage as a unit is clamped ontothedial casing through the cap screws- 33 threadedinto mounting posts 34' carried Von the base member 'l 5. It vvillrbeobviousV that the c'over' glass Biliniaybe formed from a filter glass having the qualities ofthe color lter 29 thus rendering the use of aseparate filter element unnecessary 'andfurther improving the sim- 4 plicity and sturdiness of the device. In the em` bodiment here shown, the thin sheet lter element 29 is of yellow Plexiglasf However, with either the glass filter or sheet plastic cover filter, the

mounting of the light source il substantially midway between the plane of the dial and the plane ofthe filter cover and'close to the edge of the dial and bezel opening to' permit' a compact assemblage, will not result in undue loss of radiant energy through the cover because a large portion of the light striking the bottom surface of the cover filter will be reflected back onto the dial. This alone would have the disadvantage that a considerable portion of the rays not reflected would pass through the bezel opening to annoy theY observer either as glare or by producing an apparent haze due to fluorescence of the eye if it;.were.not for the entrance of the cover filter into the combination whereby substantially all of the rays from the source striking the lter and not reflected are absorbed or blocked by the filter.

The inventiongdescribed herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the paymentV of any royalties thereon or therefor.

What is claimed is:

In an illuminated indicating instrument, a substantially non-fluorescent dial, indicia of fluorescent material and a pointer element therefor of fluorescent material, said fluorescent material fluorescing to a given color under excitation byl ultra-violet and visiblelight near the ultra-violet, a source of light rich in both ultra-violet and light near the ultra-violet situated in front of the assemblage of dial indicia and pointer for supplying radiant energyto said'fluorescent material, a filter situated between the source and the dial passing ultra-violet and visible light near the ultra-violet, and a filter-cover passing undiminished said given fluorescent color but cutting off substantially all the visible light near the .ultraviolet passed by saidvrstfilter, and said filtercover being situated in front of the entire assemblage.

GEORGE H. EVANS.

REFERENCES CITED T he following references are of record in the file of this patent:

UNITED STATES PATENTS.

Number Name Date 1,951,783 Beard Mar. 20, 1934 2,347,671 Dircksen May 2, 1944 2,347,672 Dircksen v May2, 1944 2,337,745 Garstand Dec. 28, 1943 2,029,348 Denburg v Feb. 4, 1936 2,139,707 Denburg Dec. 13, 1938 1,955,173 Chambers Apr. 17, 1934 2,311,492 Michaelis Oct. 12, 1943 2,336,560 Michaelis Dec. 14, 1943 2,310,743 Moss Feb. 9, 1943 FOREIGN PATENTS' Number Country Date 426,789 Great Britain Apr. 5, 1935 426,797 Great Britain Apr. 10, 1935 507,037 Great Britain June 8, 1939 450,513 Great Britain July 15, 1936 

